Editing Catherine Halsey

{{Era|UNSC|HCW|Post|FA}}
{{New Content}}
{{Center|For the [[SPARTAN-III Program|SPARTAN-III]], see [[Catherine-B320]]; for the [[Spartan Ops]] episode, see [[S1/Catherine]]}}
{{Character Infobox|variant=Human
|name = Catherine Halsey 
|image = [[File:Halsey Halo 4.png|275px]]
|homeworld = [[Endymion]]<ref name="haba">[[Data Drop/HABA]]</ref>
|birth = [[2492|March 19, 2492]]<ref name="alph">'''[[Halo 3: ODST]]''', map ''[[Alpha Site]]'' - [[ONI Memorial]]</ref>
|rank = 
|gender = Female<ref name="thunk">'''Halo: First Strike''', ''page 119''</ref>
|height = 170 centimeters (5 ft, 7 in)<ref name="vis">'''[[Halo: The Essential Visual Guide]]''', ''page 90''</ref>
|mass = {{Convert|56.7|kg|lb}}<ref name="vis"/>
|hair = Gray (formerly black)<ref name="thunk"/><ref name="hair and eyes" group="note">Halsey is depicted with blonde hair in both ''Halo Legends'' and the ''Halo: Combat Evolved Anniversary'' terminals. She is also depicted with green eyes in ''Legends''.</ref>
|eyes=Gray-blue<ref name="thunk"/><ref name="hair and eyes" group="note"/>
|era = *[[Insurrection]]
*[[Human-Covenant War]]
|notable = *Had a child, [[Miranda Keyes]], with the late [[Jacob Keyes]]
*Is one of the smartest women of the 26th century<ref>[[Halopedia:Letter - Dr. Halsey|Halopedia letter to Eric Nylund]]</ref>
*Types at a rate of 140 words per minute.<ref>'''[[Halo: Ghosts of Onyx]]''', page 177</ref>
|affiliation =
*[[United Nations Space Command|UNSC]]; [[Office of Naval Intelligence]] ''(former)''
*Possibly colluding with [[Covenant remnant|Covenant]] as of early [[2558]]<ref name="defection" group="note"/>
}}
{{Quote|Spartans never die? If only that were true.|Catherine Halsey, reflecting her guilt over the SPARTAN-II Program.<ref>'''''Halo: First Strike''''', ''page 249''</ref>}}

'''Catherine Elizabeth Halsey, MD, PhD''', (Civilian Consultant 409871, phonetically identified as "'''Charlie Hotel'''"),<ref>[[Halo Graphic Novel, Page 122|'''Halo Graphic Novel''', ''page 122'']]</ref> is a key scientific adviser of the [[Office of Naval Intelligence]], best known for her work with the [[SPARTAN-II Program]], developing and creating [[smart AI]]s, and for overseeing the development of the [[MJOLNIR Powered Assault Armor]]. Despite being a [[civilian]], she held considerable authority within ONI and commanded respect from important military figures.<ref name="fs123">'''''Halo: First Strike''''', ''page 123''</ref> Though generally well-regarded among her peers, she has personally endured intense guilt for condemning the Spartans to the life of a super soldier and has always held them in high esteem. After the [[Human-Covenant War]], she was stripped of her position, incarcerated, and treated as a war criminal by the UNSC at large, which led to her apparent defection to the [[Covenant remnant|reunified Covenant]].<ref>'''Spartan Ops''', episodes ''[[S1/Catherine|Catherine]]'' through ''[[S1/Exodus|Exodus]]''</ref><ref name="defection" group="note"/>

==Biography==
===Early life and career===
[[File:Halsey_self_portrait.jpg|thumb|left|150px|A self portrait of Halsey, aged eighteen.]]
Catherine Elizabeth Halsey was born on the colony world [[Endymion]], in the city of [[Port Vernon]], on [[2492|March 19th, 2492]].<ref name="haba"/> Not much is known about her early life, but what little is known gives a glimpse of what would be a promising career. In her own words, she was ''"...smarter than her parents, always reading, talking, learning, and eager to share her knowledge with anyone who would listen."''<ref>'''[[Halo: The Fall of Reach]]''', ''page 235''</ref> By [[2507]], at the age of 15, Dr. Halsey was already writing her second Doctoral Thesis paper, in which she discussed archaic line commands.<ref name="FS">'''Halo: First Strike''', page 128</ref> She was [[Vice Admiral]] [[Ysionris Jeromi]]'s star pupil as well.<ref>'''Halo: The Fall of Reach''', ''page 57''</ref>

In 2507, Halsey met [[Elias Carver|Dr. Elias Carver]] at an academic social mixer, during which Carver was discussing "the matrix mechanics of the socio-and politico-economic vectors of human expansion". Halsey saw Carver's ideas as genius but his algorithm implementation as obsolete. Carver had used only [[seven]] dimensional parameters in his calculations; Halsey thought he needed sixteen and attempted to correct him. Carver did not appreciate being challenged by a young upstart. Halsey later noted that had she known that Carver would commit suicide two years later, she would have been more charitable. However, the future [[Vice Admiral]] [[Michael Stanforth]], then a [[Captain (Navy)|Captain]], took note of Halsey. This was the start of Stanforth's continuous aiding of Dr. Halsey with her projects as her military counterpart and protecting her and her projects from those that wanted to see them disbanded in the coming decades.<ref name="journal">Dr. Halsey's personal journal</ref>

Three weeks after the occasion, the UNSC approved Halsey's grant proposal for artificial intelligence control for N-dimensional matrices, under the provision that she first successfully test a model of their choosing. It was by testing this model, using both Carver's and her own dimensional parameters, that Halsey was convinced to join the UNSC and work to end the Insurrection.<ref name="journal"/>

In August [[2510]], Halsey purchased a small, hardback [[Dr. Halsey's personal journal|journal]] in a shop on [[Reach]], near the base she was stationed in. Halsey used the journal as a medium through which to express her thoughts and concerns, as well as important research notes, and would do so for another forty-two years, until she abandoned it during her escape from [[SWORD Base]]. The journal was later recovered by ONI in [[2553]], and was designated top secret.<ref name="journal"/>

Dr. Halsey served as a scientific adviser for to the [[Office of Naval Intelligence]] from [[2515]] to [[2522]], when she was made chief scientist. She made huge contributions to many ONI Section III projects, including the creation and deployment of AI constructs. At some point, she supervised the creation of the template for third-generation [[smart AI]]s.<ref name="FS"/> She also created and initiated the SPARTAN-II project as well as the development of the MJOLNIR armor system. These all proved to be important developments for the UNSC, and to the continued survival of mankind.<ref name="journal"/> During her service with ONI, Halsey was stationed primarily on the planet [[Reach]]. By [[2551]], she lived in the community of [[Csongrád]].<ref name="haba"/>

[[Image:YoungKeyes.png|250px|thumb|right|Jacob Keyes accompanies Dr. Halsey.]]During their survey travels for the SPARTAN-II candidates, Halsey grew attached to [[Jacob Keyes]]. In November [[2524]] the two were reunited while attending a conference at the [[University of Calippus]], and the two conceived a child. In [[2525]], Halsey gave birth to [[Miranda Keyes|Miranda]] and raised her for a few years, when on July 12, [[2531]], Miranda's father agreed to take her in, raising her on [[Luna]]. Halsey would later have a falling-out with Miranda, who would later change her legal name to her father's and refuse to speak to Halsey for several years. Nonetheless, Halsey cared for her daughter and attempted to dissuade her from following her father's footsteps and joining the military, to no avail. Hoping to keep Miranda safe, Halsey used her influence within the UNSC to have her assigned to a remote post aboard the science vessel {{UNSCShip|Hilbert}}; however, Miranda and the ''Hilbert'' would play a crucial role in [[Battle of Gamma Pavonis VII|battle]], and she was subsequently assigned to various front-line posts. Though Miranda eventually invited Halsey to her promotion ceremony in [[2550]], Halsey chose not to attend.<ref name="journal"/>

Halsey served as a mentor to Professor [[Ellen Anders]] at some point prior to [[2531]], though they apparently had a major falling out, as noted by Anders, saying "Why mention Halsey here? She hated me and I hated her."<ref>'''[[Halo Wars]]''' ''manual, character profiles''</ref>

===SPARTAN-II Program===
{{Main|SPARTAN-II Program}}
{{quote|[[John-117|This boy]] could be more useful to the UNSC than a fleet of [[UNSC destroyer|destroyer]]s, a thousand [[Lieutenant, Junior Grade|Junior Grade Lieutenants]] -- or even ''me''. In the end, the child may be the only thing that makes ''any'' difference.|Halsey speaking to [[Jacob Keyes|Lt. Jr. Grade Jacob Keyes]], referring to [[John-117]] in [[Elysium City]].}}

[[File:Halsey 2.jpg|225px|thumb|left|Halsey overlooking [[Daisy-023]]'s Spartan augmentations.]]Halsey began her work on the SPARTAN and MJOLNIR programs in 2511, improving upon the shortcomings of the [[ORION project]].<ref name="journal"/> In [[2517]], at the age of 25, built a set of rigorous genetic requirements that any potential candidate of the program was required to meet. From these requirements, she identified 150 candidates, but ONI would only give her enough funding to train 75 of them. Time constraints made it impossible for her to personally screen every candidate from the Outer Colonies, so she delegated much of the responsibility to her team, while she processed candidates in [[FLEETCOM Sector Four|Sector 4]].<ref name="journal"/> [[Lieutenant, Junior Grade|Junior Lieutenant]] [[Jacob Keyes]] accompanied her as an attaché during the majority of these interviews, including most notably that of [[John-117]]. Halsey then had the children secretly brought to the planet [[Reach]] for training. The 'recruited' children were replaced with [[flash cloning|flash clones]], all of whom died due to various neurological and physiological diseases that were the natural side effects of making an entire human flash clone. In the early stages of the program, Halsey attempted to cover up the program's use of flash clones, both by withholding information from [[Admiral]] [[Margaret Parangosky]] and by using one of her AIs to cover fiscal evidence;<ref>'''Halo: Glasslands''', ''page 345''</ref><ref group="note">Halsey's attempt to hide the cloning aspect of the program would have had to have occurred in its conceptual phase, as it would have been impossible to cover up when the cloning was put into practice; even if Halsey did manage to hide the data involving the funding, numerous ONI operatives and scientists were involved in the replacement operation and Halsey was not in a position to keep them from relaying the information to Parangosky. In addition, with ONI constantly monitoring the progress of the program, Halsey would have had no way to keep such a large-scale operation secret in the long term.</ref> Parangosky eventually discovered the cloning scheme, which would contribute to Halsey's arrest by ONI decades later.<ref name="clones" group="note">This seems to exhibit a double standard on Parangosky's part, as she had authorized the deaths of hundreds of children through the SPARTAN-III Program. However, Parangosky viewed the SPARTAN-IIIs as a necessary sacrifice, whereas the use of flash clones was not strictly necessary and caused excessive trauma to the already beleaguered parents of the SPARTAN-II candidates. Though she was angered by Halsey's refusal to admit the use of flash clones, her true quarrel with the doctor was based on her motivation for using the clones. While Halsey insisted that the flash clone project was meant to ease the parents' suffering and stifle suspicion, Parangosky was adamant that it was intended, (perhaps subconsciously), to ease Halsey's guilt and comfort her ego.</ref>

With the assistance of [[Chief Petty Officer]] [[Franklin Mendez]] and the AI [[Déjà]], she proceeded to train the Spartans. She supervised their augmentation procedures, combat training, and education, and studied the effects of the Spartan lifestyle on the children. She kept in close contact with them all throughout their lifetimes, from her base under Reach. To the minor annoyance of the Spartans Dr. Halsey was capable of identifying them even underneath heavy combat gear or their MJOLNIR armor, and used their first names to prove this time and again. The Spartans held considerable respect for Dr. Halsey, (with [[Jorge-052|one]] stating that he had been ''"All hers half [his] life"''),<ref>'''Halo: Reach''', campaign level ''[[ONI: Sword Base]]''</ref> and would follow her orders and suggestions in the absence of those from a superior officer. The doctor was also privy to many of the recruits' secrets, having taught several to them as children, such as the ''[[Oly Oly Oxen Free]]'' security tune.<ref name="thunk"/>

===Involvement during Human-Covenant War===
====Battle of Harvest====
{{Main|First Battle of Harvest}}
After first contact with the [[Covenant]], Dr. Halsey accessed [[Lieutenant Commander|LCDR]] [[Jilan al-Cygni|al-Cygni]]'s ONI [[sloop]] ''[[UNSC Walk of Shame|Walk of Shame]]'''s data archive. During Dr. Halsey's investigation, she began researching the last conversations of the AI [[Mack]], and his choice of misspelled Shakespeare during his last days of rampancy.<ref>'''[[Halo: Contact Harvest]]''', ''page 391''</ref>

====Next class of Spartans====
Despite ONI's intentions to continue with the SPARTAN-II program, Dr. Halsey began having difficulty finding a suitably large number of candidates that fit her genetic and age profiles. Additionally, most of her budget was now being used to maintain the MJOLNIR armor in service. Eventually, ONI discontinued the SPARTAN-II program, reassigned most of its personnel to other projects (such as the [[SPARTAN-III Program]]), and buried Halsey in [[CASTLE Base]], cutting off her access to classified material. However, in just a few short years, her SPARTANs would prove themselves to be the most effective weapon the UNSC had against the Covenant. ONI's reticence vanished, her budget mushroomed overnight, and she was offered a corner office in [[Olympic Tower]] in [[New Alexandria]]. However, Halsey decided to remain in CASTLE as a means of revenge against ONI, which would now have to spend half the day going through security checks.<ref name="tfor castle">'''Halo: The Fall of Reach''', '''2010''', ''pages 261-262''</ref>

====Capture====
{{Main|Raid on the Third Fleet of Glorious Consequence}}
[[File:Halsey n' John.jpg|250px|thumb|right|Catherine and John-117 face [[Thel 'Lodamee]] on a [[Covenant assault carrier]], ''[[Resplendent Fervor]]'']]
In [[2544]], Halsey was captured by the Covenant's ''[[Third Fleet of Glorious Consequence]]'' during the [[Battle of Miridem]], while she was [[cryonics|cryonically frozen]].<ref>'''[[Halo: The Fall of Reach|Halo: The Fall of Reach (2010)]]''', ''Adjunct''</ref> A team of SPARTAN-IIs, consisting of John-117, [[Kelly-087]], [[Frederic-104]], [[Solomon-069]], and [[Arthur-079]] were sent to rescue her with [[Open Frame 92/Extra-Vehicular Activity|OFA92/EVA "Booster Frame"]] vehicles. Knowing Halsey's value to both the UNSC and the Covenant, [[Fleet Master]] [[Luro 'Taralumee]] planted decoys in several of the fleet's [[CCS-class battlecruiser]]s.

Solomon was killed by one of these decoys, which was actually an [[antimatter charge]] giving off a false signal. Arthur was also killed, crushed between two cruisers while covering Kelly-087 from multiple pursuing [[Type-31 Exoatmospheric Multi-role Fighter|Seraph fighters]]. After finding the ship Halsey was on, John, Kelly and Fred fought through large numbers of Covenant forces, though Fred and Kelly were separated during the fight. John soon reached Halsey and rescued her from a cryo pod, but the two were immediately stopped by [[Sangheili Major|Major]] [[Thel 'Lodamee]]. Halsey watched as John engaged the Elite in an [[Type-1 Energy Weapon/Sword|energy sword]] duel. However, Fleet Master 'Taralumee [[Modular Dispersal Technology|detached]] the section of the ship they were in, retrieving Thel mid-fight via [[gravity lift]], and jumped into Slipspace.

Halsey and John entered an [[Covenant escape pod|escape pod]] but were engaged by Seraph fighters. They were soon rescued by Fred and Kelly, who had captured a Seraph fighter. The surviving humans were then recovered by the [[ONI PRO-49776|stealth ship]] that had deployed the Spartans. Aboard the stealth ship, Halsey comforted John as he swore not to lose another Spartan.

====Private projects====
Over the course of the war, Halsey worked with her AIs experimenting on new ways to extend the life of smart AI and expand their processing capabilities. She also experimented on her private smart AI "triumvirate", where three AI constructs, arranged in parallel, could divide their algorithms and would decide matters by majority vote. Coincidentally, a similar arrangement was already in use by the [[Assembly]], a group of AIs that kept its existence hidden from humans. In [[2547]], after thoroughly researching the subject, she stole the decommissioned [[Shaw-Fujikawa Translight Engine|Slipspace drive]] of the {{UNSCShip|Tripping Light}}, and conducted an experiment on building an abstract fractal in the volume of [[Slipstream space]], in an attempt to create a virtually infinite processing matrix for AIs to inhabit. Though the test was ultimately a failure, the Assembly saw the potential in the concept of residing permanently in the alternate space-time.<ref name="journal"/><ref>'''Halo: Reach''', ''[[Data pads|Data pad 17]]''</ref>

====Fall of Reach====
{{Main|Fall of Reach}}
{{Quote|We knew this day would come. They have found our fortress among the stars. The Covenant are on Reach. They will burn this planet, kill millions, and when Reach falls - and fall it will - there will be nothing left to stand between them and Earth. Yet, even in our darkest hour, hope remains. Now, who will protect it? Show me Noble Team.|Catherine Halsey during her discussion with Cortana about the plans for her safe delivery.}}
[[File:HReach - Carter and Halsey.png|250px|left|thumb|Dr. Halsey finally meeting a [[SPARTAN-III Program|SPARTAN-III]].]]

In 2552, Halsey was researching various [[Forerunner]] discoveries made on [[Reach]], including an excavation for an [[Babd Catha Forerunner complex|underground Forerunner facility]] beneath ONI's [[SWORD Base]] and artifacts discovered in [[Visegrád]] by Professor [[Laszlo Sorvad]], a civilian [[xenoarchaeology|xenoarchaeologist]] in the employ of ONI, although her permanent private office remained in [[CASTLE Base]].<ref name="tfor castle"/>

During the opening stages of the [[Fall of Reach]] on [[2552#July|July 26, 2552]], Halsey was working on the excavation site beneath SWORD Base, when the facility came under attack by a [[SDV-class heavy corvette|Covenant corvette]]. After the destruction of the corvette, she called [[NOBLE Team]] to her laboratory for debriefing, where she learned of the death of Professor Sorvad at the hands of a [[Sangheili Zealot]] survey team. After arguing with [[Carter-A259]] over Noble's failure to apprehend the Elites' leader and [[Catherine-B320]]'s attempted access of restricted files, she learned of the nature of Sorvad's "latchkey" discovery, a way to decipher data found in the Forerunner complex beneath Sword Base. After dismissing Noble Team, she began the decryption process of the "latchkey" data in the Forerunner complex.

On August 3, Halsey split up Cortana, assigning her "copy" to work on the decryption of the Forerunner data in the underground facility below Sword Base, while her other half would prepare for the Spartans' mission; [[Operation: RED FLAG]]. When the {{UNSCShip|Iroquois}} arrived at Reach from [[Battle of Sigma Octanus IV|Sigma Octanus]] on August 12, Halsey visited the ship. During her visit, Captain Keyes came to see her, and they discussed their daughter Miranda, the [[Keyes Loop]], the Spartans and Operation RED FLAG. Later in the day, she visited [[Camp Hathcock]] to see John-117 after his debriefing. She was evidently working underneath SWORD Base when the facility was bombarded by the Covenant on August 14,<ref>'''Halo: Reach''', campaign level ''[[Long Night of Solace (level)|Long Night of Solace]]''</ref> although she survived the assault and later checked in her office in CASTLE Base to discuss the specifics of RED FLAG with Cortana on August 25.<ref name="tfor castle"/> Two days later, she met most of the remaining Spartan-IIs at the FLEETCOM military complex in the briefing for RED FLAG.<ref name="journal"/>

[[File:Halsey n' Six.jpg|thumb|250px|right|Halsey hands Cortana's fragment to SPARTAN-B312.]]On August 29, she was present in the first test of "smart" AI integration with [[MJOLNIR Powered Assault Armor/Mark V|MJOLNIR Mark V armor]]. Although John-117 and Cortana were nearly killed as a result of Colonel Ackerson's involvement, the test was ultimately successful. After the test, Halsey sent an official protest, backed by [[Vice Admiral]] [[Michael Stanforth|Stanforth]], to {{UNSCShip|Burden of Proof}}, suggesting that Ackerson may have suffered a mental breakdown and recommended that he be taken into custody.<ref name="journal"/> Later that day, Halsey returned to her work in the SWORD Base excavation and had NOBLE Team sent to SWORD Base with a pretext of orders to destroy the facility.<ref name="thepackage">'''Halo: Reach''', campaign level ''[[The Package (level)|The Package]]''</ref>

Once Noble Team had arrived at SWORD, Halsey revealed Noble's true orders to them: to transport [[The Package (data storage unit)|a package]] containing "mankind's best chance for survival" to the Halcyon-class cruiser ''[[UNSC Pillar of Autumn|Pillar of Autumn]]'', holding position in the [[Aszod ship breaking yards]]. After Noble's successful defense of her lab while she prepared the package, she entrusted [[SPARTAN-B312]] with the package: a fragment of the AI [[Cortana]], now uploaded with the information from the Forerunner facility. Once she made certain that Noble Six would deliver Cortana to the ''Autumn'', she left for CASTLE Base under the escort of Jun-A226 while the remaining Noble Team members delivered package to the ''Autumn''.<ref name="thepackage"/><ref name="journal"/>

====Refuge under CASTLE Base====
After arriving at ONI's [[CASTLE Base]], Halsey volunteered to remain behind to ensure that all UNSC technology was secured from possible capture.<ref>'''Halo: First Strike''', ''page 125''</ref> She initiated [[Operation: WHITE GLOVE]], destroying several [[Artificial intelligence|AIs]] (including [[Cortana]]'s "older sister" [[Kalmiya]]) to keep the Covenant from accessing UNSC databases. With expectations that the Covenant would glass the planet and knowledge that even if they didn't, she would be facing an entire army of Covenant ground forces, it was clearly an offer of sacrifice.

However, this changed when Spartans [[Fred-104]], [[Kelly-087]], [[Vinh-030]], [[Isaac-039]], and [[William-043|Will-043]] appeared at the entrance to CASTLE Base. With the firepower to potentially fight their way out, the possibility of surviving CASTLE Base's destruction became available. She gave emergency aid to the Spartans for their injuries, but a data anomaly detected by her accompanying AI, [[Kalmiya]], attracted Dr. Halsey's attention.

The data had been accessed by [[Araqiel]], an AI that worked for [[Colonel]] [[James Ackerson|Ackerson]], one of Dr. Halsey's main competitors within ONI. After tracing the data access, Dr. Halsey stumbled across the AI, left behind by its master. Araqiel then proceeded to threaten her (he went as far as telling her he would fill the room with poison, and that she would be reported). She started typing in "archaic line commands" to access his code directory and personal fail-safe. She then shut him down.<ref name="Combo">'''Halo: First Strike''' pages 127-128</ref> After shutting it down, she proceeded to read through Ackerson's files and discovered a number of things including the location of [[Onyx]], evidence of the [[SPARTAN-III Program]] and a map of the mining tunnels CASTLE base had been built upon. The latter particularly interested the Doctor as the file had been classified at X-Ray level, making the file abnormally important for ancient maps. From this, she deduced that there was something of importance under the mountain.

Assuming that at the very least these maps provided a backdoor, she chose to move the Spartans out of the base and into the mineshafts. She then triggered CASTLE Base's self-destruct mechanism and activated the fail-safe on Kalmiya. With the Spartans in tow, they moved into the mineshafts.

Over the course of the next five days, the Spartans and Dr Halsey searched the mines, looking for either an exit or what Dr. Halsey would dub ''"the most important discovery of the millennium"''. On the fifth day, Fred discovered an entrance into a large [[Forerunner]] [[Menachite Forerunner complex|structure]], and within, the [[Forerunner crystal]]. However, the acquiring of the crystal sent a spike of neutrino radiation, attracting the attention of the Covenant. Their location was now threatened by Covenant forces.

Following a Covenant attack, Halsey and her team retreated into a hallway and sealed off the entrance, losing contact with Isaac and Vinh in the process. However, they quickly discovered that the hallway was a dead end. It is presumed that Halsey and the surviving Spartans remained stranded at this location for some time.

====Escape from Reach====
{{Main|Raid on Reach}}
Days later, a group of Spartans, including John-117, rescued Dr. Halsey and the remaining Spartans and evacuated them from Reach to the captured ''[[Ascendant Justice]]''.

[[File:Halsey Mem.jpg|250px|right|thumb|Dr. Halsey's ONI memorial plaque.]]Dr. Halsey later saw the importance of destroying this artifact after it caused a [[Slipstream space|Slipspace]] anomaly that nearly resulted in the destruction of the ''Ascendant Justice''. After escaping Reach, the group fled to [[Eridanus Secundus]] in the [[Eridanus system]]'s asteroid belt, where the Spartan's [[Assault on Eridanus Secundus|first mission]] had been in. While there, she stole the [[Jacob Jiles|rebel governor]]'s spacecraft ''[[Beatrice]]'' and, along with [[Kelly-087]], whom she had sedated, escaped into Slipspace. When asked by Admiral Whitcomb as to the reasons for her actions, she gave a simple UNSC code Three-Nine-Two, which meant that she was on a high priority mission. She entrusted the Forerunner crystal to [[Corporal]] [[Locklear]], telling him to keep it safe, hidden, and to do whatever it took to keep it from falling into enemy hands; otherwise the Covenant might gain unprecedented advances to their already sophisticated slipspace technology. Soon after, the Corporal destroyed the crystal, dying in the ensuing explosion. The Covenant later recovered a few fragments.<ref>'''Halo: First Strike''', ''page 339-340''</ref>

In the aftermath of the battle, she was presumed dead by the Office of Naval Intelligence and honored, with other personnel, on a plaque at [[ONI Alpha Site]]. Some in ONI knew she had survived, though, and Director Parangosky later maintained this false declaration of death to be able to keep Halsey hidden from the public.

====Battle of Onyx====
{{Main|Battle of Onyx}}
Dr. Halsey and Kelly eventually arrived at Onyx, while reuniting with [[Senior Chief Petty Officer|SCPO]] Mendez and eventually her remaining SPARTAN-II's and the [[SPARTAN-III Program|SPARTAN-III]]'s. Contacting the ONI AI [[Endless Summer]], she utilized Onyx's [[slipspace COM launcher]] and Cortana's slipspace transmission from [[Installation 05]] as a carrier wave to send a message to Earth, in which she requested [[Terrence Hood|Lord Hood]] to send more Spartans to secure Forerunner technology on Onyx.

She helped decipher the mystery of the planet. At first, she tried to maintain secrecy about her intentions out of habit, until [[Kurt Ambrose]] confronted her about it. She admitted that she was not actually looking for Forerunner technology or weapons, but rather the secret Forerunner [[shield world]], which she believed to be equivalent to a bomb shelter, and would be capable of keeping the remaining Spartans safe to evade all current war and let them live to fight another day.<ref>'''Halo: Ghosts of Onyx''', ''page 341-343''</ref> Her relative expertise with Forerunner technology was vital to the survival of the UNSC forces on the planet, as she was able to interpret Forerunner glyphs when navigating the facility, guiding the Spartans to the facility's [[Cartographer|map room]], as well as allowing them to quickly move across the megastructure by using its [[teleportation grid]].

At the end of the battle, she, along with Mendez, [[Blue Team]], and the Spartan-III survivors, retreated inside the shield world known to the Forerunners as [[Trevelyan|Shield World 006]], which she correctly deduced to be a [[Dyson sphere|"micro" Dyson sphere]], enclosed outside normal space-time within a slipspace bubble.<ref>'''Halo: Ghosts of Onyx''', ''page 380-381''</ref>

Dr. Halsey, Chief Mendez and the surviving Spartans explored the Dyson sphere for some time, coming across several Forerunner structures and a hangar full of Forerunner vessels. Halsey recognized the potential of scavenging the technology in these ships and using it to improve the precision of human slipspace drives, among many other advances that could be gleaned from artifacts across the shield world.<ref>'''Halo: Glasslands''', ''page 366-367''</ref>

===Post-war===
====Arrested====
{{Quote|My Spartans are humanity's next step – our destiny as a species. Do not underestimate them. But most of all, do not underestimate... [[John-117|him]].|Halsey to her interrogator after her arrest.}}
[[File:Halsey Interrogated.png|left|275px|thumb|Halsey was interrogated many times after the war.]]Halsey and the others were eventually rescued from the shield world, but Halsey was immediately arrested by [[Captain (Navy)|Captain]] [[Serin Osman]] under CINCONI [[Admiral]] [[Margaret Parangosky]]'s orders, for "committing acts likely to aid the enemy" by stealing the ''Beatrice'', kidnapping Kelly-087 and telling Lord Hood to send more Spartans to Onyx - all with the sole intention of hiding in the shield world until the war was over. Even though Halsey had provided the UNSC with new Forerunner technology as promised, the circumstances conveniently allowed Parangosky finally carry out her personal vendetta against Halsey. Consequently, in [[2553#March|March 2553]], Parangosky detained Halsey on the newly-established [[Ivanoff Station]], in orbit around [[Installation 03]], and personally interrogated her, accusing Halsey of not informing her of the use of flash clones at the onset of the SPARTAN-II Program.<ref name="clones" group="note"/> As far as the public is concerned, Halsey was killed during the [[Fall of Reach]] until Parangosky decides otherwise.<ref>'''Halo: Glasslands''', ''page 341''</ref>

Following this she was treated as a war criminal and interrogated by many ONI personnel, including one mysterious individual who knew of the SPARTAN-II Program but did not seem to be Naval Intelligence.<ref>'''[[Halo 4]]''', campaign level ''[[Prologue]]'' ('''Halsey''': ''"What are you after? The other before you were Naval Intelligence but you, you're something else."'')</ref> Halsey told him the details of their creation just as she had told many before him, responding to his accusations about the project's immorality. According to her, her actions were justified by the Great War, since without Spartans it could have never been won. While the interrogator belittled the importance of the SPARTAN-IIs, going so far as to claim that they accomplished their victories because they lacked basic humanity, Halsey retained her confidence in their abilities, stating that her Spartans were "humanity's next step" and "our destiny as a species". To prove this, she predicted John-117 would return, who she firmly believed was alive.

In March 2553, she had been released from Ivanoff Station and was stationed aboard the {{UNSCShip|Infinity}}, working on incorporating the newly-discovered Forerunner technology to the ship. <ref>'''Halo: The Thursday War'''</ref> After the ''Infinity'' participated in the [[Sangheili civil war]], Halsey was approached by [[Black-Box]], who requested her assistance in re-integrating a damaged fragment of himself into his core matrix. However, Halsey stated that she was unable to help him.<ref>'''Halo: The Thursday War''', ''page 358''</ref> Halsey was returned to Ivanoff at the first opportunity by order of Admiral Parangosky. She was working on the station on [[2554|December 15, 2554]], when the ONI scientists, whom she considered unqualified for their job, recovered the Forerunner device known as the [[Composer]] on Installation 03. Halsey was fascinated by the similarities between the artifact and the AI matrix compiler used by the UNSC to create smart AIs, particularly because the compiler was of her own design.<ref>'''Halo 4''', campaign level ''[[Composer (level)|Composer]]'', [[Halo 4 audio logs|Audio log]]''</ref>

====Return to ''Infinity''====
{{Quote|Life is too short. I will never learn all that exists in our own tiny galaxy, let alone the rest of the universe. And I so desperately want to know ''everything''. But the UNSC acts like children at play in a sandbox. Mistaking its edges for the limits of the world.|Catherine Halsey to Captain Thomas Lasky regarding her subterfuge.}}
[[File:Halsey Infinity.png|right|thumb|250px|Halsey examines the recovered Forerunner artifact.]]Halsey was later returned aboard the ''Infinity'' during the ship's [[Second Battle of Requiem|second expedition]] to the Forerunner shield world [[Requiem]] in [[2558]] as her unique expertise was required to study a [[Requiem translocation artifact|mysterious Forerunner artifact]]. Many of the crew had mixed feelings about bringing her aboard, [[Sarah Palmer]] suspicious of her and feeling she might try to sabotage the ship, [[Thomas Lasky]] sharing her worries but feeling there was no choice. Halsey was unimpressed by the SPARTAN-IVs assigned to guard her, wryly questioning their competence and general attitude. Upon arriving on the ''Infinity'' aboard the [[UNSC prowler|prowler]] {{UNSCShip|Aladdin}}, she demanded she be uncuffed before examining the artifact. With a few gestures from her, the artifact began reacting to her, she translating its actions as signs that she should examine the ship's engines. Upon doing so, her conclusion was that the artifact was "communicating" with multiple parts of the ship and transmitting to Requiem. Some time later, she analyzed a Forerunner [[beam emitter|beam tower]] encountered by [[Fireteam Crimson]] in the location codenamed [[Two Giants]].<ref>'''Spartan Ops''', [[S1/Catherine|S1E3 ''Catherine'']]</ref>

Sometime later, she was escorted by [[Gabriel Thorne]] who volunteered to be her security while she continued her research on the Forerunner artifact. As Thorne questioned her about the Spartan-II program, she was contacted by an unknown person about the Prometheans.<ref>[[Spartan Ops|'''Spartan Ops''']], [[S1/Didact's Hand|S1E4 ''Didact's Hand'']]</ref> When Fireteam Majestic brought back the "[[Didact's Gift]]", Halsey noted its design resembled an A.I. matrix. Upon activating it, it caused the screens in the lab to show memories of [[New Phoenix]], with one of those memories being the Forerunner artifact. Speculating that she had misinterpreted the translocation artifact's true nature, she proceeded to further examine it. Again, she was contacted by the unknown person through her data pad, who, unbeknownst to her, was [[Jul 'Mdama]]. Suspicious of who Halsey was communicating with, Sarah Palmer confiscated her data pad, and gave it to Lasky, who then ordered Halsey to be taken into custody.<ref>'''Spartan Ops''', [[S1/Memento Mori|S1E5 ''Memento Mori'']]</ref>

After a short interrogation, Halsey was returned to her prison cell.<ref>'''Spartan Ops''', [[S1/Scattered|S1E5 ''Scattered'']]</ref> When Roland entered the cell to ask her questions, Halsey took her chance and overrode Roland's protocol, allowing her to control him. Using his authority to be escorted to Lasky's office, Halsey accessed the data onboard ''Infinity'' to find out what had been kept from her, eventually finding that they had kept secret the return of John-117. Infuriated, Halsey contacted 'Mdama, informing that she had deduced he was her helper but that their alliance could free the Librarian. However, Roland was able to restore himself to his normal state and cut off the connection, and Halsey was promptly arrested. When Halsey was brought to Lasky, she slapped the captain lividly, scolding him for not telling her Spartan was alive. The two were interrupted, however, when Promethean forces gained access to the interior of ''Infinity''. Fending off the Prometheans with his Marines, Captain Lasky picked up Halsey and attempted to escort her to safety.<ref>'''Spartan Ops''', [[S1/Invasion|S1E7 ''Invasion'']]</ref>

====Capture and possible defection====
Late in the attack, though, Halsey was kidnapped by a Promethean Knight and teleported to Requiem. When Admiral Serin Osman was informed of this abduction, she chose to finally enact Parangosky's wishes and ordered for Halsey's immediate termination.<ref name="Spops8">'''Spartan Ops''', [[S1/Expendable|S1E8 ''Expendable'']]</ref>

[[File:H4-SOps-Halsey-Librarian-1.jpg|thumb|250px|Dr. Halsey meets the [[Librarian]], and learns of the Forerunner artifacts all over the galaxy.]]Halsey was then taken to the site of the Librarian, where Jul 'Mdama had her disable the shield previously erected during Doctor Glassman's attempts to access the shrine. As the shield deactivated, she quickly entered the beam of light being produced by the shrine, to 'Mdama's great anger.<ref name="Spops8"></ref> There, she met the Librarian and was given the [[Janus Key]], which gave the location of every Forerunner artifact in the galaxy. After taking it, she returned to the shrine, where 'Mdama acquired one half of the key. The intervention of Palmer and Fireteam Majestic forced 'Mdama to retreat from the site with Halsey - now suffering from a gunshot wound to the shoulder - but not before she threw the key's other half to Thorne.<ref>''[[Spartan Ops]]: [[S1/Key|S1E9 ''Key'']]</ref> Halsey fell unconscious due to her wound and was transported to a Covenant ship, where her left arm was amputated. Later, 'Mdama told Halsey that he should have killed her for betraying him, but Halsey replied that the UNSC had tried to kill her as well. She agreed to help the Covenant, ambiguously claiming that she wanted revenge.<ref>''[[Spartan Ops]]: [[S1/Exodus|S1E10 ''Exodus'']]</ref><ref name="defection" group="note">According to Brian Reed, the lead writer of ''Spartan Ops'', the object of Dr. Halsey's revenge was originally clear-cut: Commander Palmer and the crew of ''Infinity''. However, this plot point was considered too blatant and out of character. To better depict Halsey's signature "double talk", this was changed to the less obvious presentation used in the final draft. During [http://blogs.halowaypoint.com/Headlines/post/2013/03/04/Spartan-Ops-Episode-Review.aspx his review of Season 1], Reed suggested that Halsey's grudge may be against Commander Palmer specifically, the UNSC as a whole, or "everyone" in general. However, he implied that she was actually making a veiled threat toward Jul 'Mdama; in this case, her apparent defection would merely be a ruse.</ref>

====Eulogy for Noble Six====
At some point after the Human-Covenant War, Halsey gave a eulogy for [[SPARTAN-B312]], in which she commended the Spartan's courage and sacrifice. She noted that Noble Six's choice to remain behind in Aszod allowed humanity to discover the Halos, ultimately leading to victory against the Covenant.<ref>'''Halo: Reach''', campaign level ''[[Lone Wolf]]''</ref>
{{Clear}}
==Personality and traits==
[[File:FoR - Ackerson n Halsey.png|left|thumb|225px|Halsey and her rival, Colonel James Ackerson.]]
Halsey's intelligence is unquestionable as well as the loyalty and respect she receives from the majority of her comrades and her Spartans. However, her judgment is not always correct, although bearing the guilt of the Spartan program, her sense of right and wrong has differed greatly. It is obvious that she truly cares about her Spartans, to the point she was ready to give up everything in order to save them by sheltering them in the shield world.

Halsey has been shown to be extremely devoted to her work and personal goals, and she rarely partakes in any social activities. Though she had distanced herself from most of her friends from her youth, she would often browse through casualty lists within the [[UNSC subnet]], finding the majority of them dead by the final years of the war. Eventually, she came to consider her AIs the closest friends she has and prefers their company.<ref name="journal"/> Although she may be angered easily at being mentally defeated, she always appreciates the simplicity of them. None more than [[Cortana]], who was actually created from a flash clone of her own brain. She is an atheist, lacking belief in the existence of any god.<ref>'''Halo: Ghosts of Onyx''', ''page 157''</ref>

Halsey has a notable fondness for classical music, especially [[Wikipedia:Claude Debussy|Debussy]], and often asks nearby AIs to play select pieces as she works.<ref>'''Halo: Ghosts of Onyx''', ''page 148''</ref> She has a bad habit of keeping a messy office and drinking cold coffee, tending to prepare the drink and then become distracted by work, only remembering it hours, sometimes days, later.<ref>'''Halo: The Fall of Reach''', ''page 230''</ref><ref>'''Halo: First Strike''', ''pages 125-126''</ref> She preferred darker coffees than those grown on Reach.<ref>'''Dr. Halsey's personal journal''', ''December 4, 2510''</ref> On January 9, [[2535]] she met with [[Chief Petty Officer]] [[J. G. Jimes]] in order to procure quality Beniese coffee.<ref>'''Dr. Halsey's personal journal''', ''January 7, 2535''</ref>

Halsey's projects and the results they yielded gained her widespread acclaim and sympathies among many high-ranking members of the UNSC military, such as [[Admiral]] [[Michael Stanforth|Stanforth]] and [[Fleet Admiral]] [[Terrence Hood|Hood]]. However, she also garnered a number of competitors and opponents over the decades. The most notable of her rivals was [[Colonel]] [[James Ackerson|Ackerson]], who constantly tried to spy on her and co-opted her work while attempting to sabotage the SPARTAN-II Program. In addition, ONI Commander-in-Chief Admiral Margaret Parangosky was resentful of Halsey, only tolerating her because she was so crucial to the war effort,<ref>'''Halo: Ghosts of Onyx''', ''page 48''</ref> but had her detained immediately after the end of the war. Parangosky's antipathy for Halsey was passed on to [[Serin Osman]], a Spartan-II washout whom the Admiral specifically indoctrinated and groomed to become her successor to secure her personal legacy within ONI.

Halsey remained rather indifferent to her parents' deaths when Endymion was glassed, as she had not seen them in years and had grown aloof from them.<ref>'''Halo: Glasslands''', ''page ???''</ref>
{{Clear}}
===SPARTAN-II Program and guilt===
[[File:Halsey Eyes.png|thumb|right|300px|Halsey battled guilt over the SPARTAN-II project. She knew that moral lines had been crossed to save humanity.]]Dr. Halsey carried extraordinary guilt because of the [[SPARTAN-II Program|SPARTAN-II project]], in the feeling that she had exploited the children and destroyed their lives. Though she continued to support them and gained monumental prestige for her efforts, she also felt responsible for each one who died. Despite being devoted to preventing the looming threat of the Insurrection escalating into a massive war which could potentially destroy human civilization,<ref name="journal"/> she never could quite justify the Spartan candidates' exploitation as a "necessary sacrifice".

At the conceptual phase of the SPARTAN-II Project, Halsey evidently failed to fully understand its moral implications; she was constantly revolted upon seeing her work in practice, and the notion of "sacrificing the few to save the many" rarely worked to soothe her conscience.<ref>'''Halo: The Fall of Reach''', ''page 28''</ref> While she attempted to maintain a professional distance to the SPARTAN-II candidates, she could never bring herself to view them as mere test subjects and always addressed them by their first names.<ref>'''Halo: The Fall of Reach''', ''pages 26, 54''</ref> She held considerable respect for the Spartans, and easily recognized them even with their armor on, which seemed to greatly annoy them.<ref>'''Halo: First Strike''', ''pages 120-121''</ref>

Due to her burdened conscience, Halsey was consistently at odds with ONI Section Three over the course of the SPARTAN-II Program. ONI was not appreciative of hesitation or delays in what they viewed as their prize project, and constantly pressured Halsey to implement easier and more straightforward - and often also more unethical - solutions, while Halsey tried to do her best to ensure the safety of the candidates,<ref>'''Halo: The Fall of Reach''', ''page 29''</ref> despite knowing that she could not save them all. While an ONI representative had labeled the Spartan washouts as "acceptable losses", Halsey did not view any of them as acceptable.<ref>'''Halo: The Fall of Reach''', ''page 31''</ref> Even at the onset of the augmentation procedures, which she knew would kill or cripple a large portion of the candidates, she was considering that they should take more time to test the chemicals before applying them. However, [[Déjà]] pointed out that if she proceeded too slowly and ONI detected a delay, they might replace Halsey with someone who "harbored fewer doubts" - and most likely someone less qualified as well, prompting Halsey to stay on board with the project for the sake of the candidates' safety.<ref>'''Halo: The Fall of Reach''', ''page 58''</ref>

By the time she was rescued from Reach by the ''Ascendant Justice'', she simply wanted to save as many lives as she could, believing that the war was not one that the UNSC could possibly win. While she knew that her own Spartans, the SPARTAN-IIs, couldn't be persuaded to turn from the war, she believed the SPARTAN-IIIs may not yet have been fully determined to win the war, and she set out to try and weaken their resolve to fight. In a similar case (as revealed in her chat with [[Gabriel Thorne]]), she also believed that the [[SPARTAN-IV Program|SPARTAN-IVs]] were incapable of being Spartans, although she did reveal that Thorne was the closest to a full Spartan out of all the IVs.<ref name="Ep2">'''[[Spartan Ops]]''', ''[[S1/Didact's Hand|S1E4 Didact's Hand]]''</ref>

===John-117===
[[File:Mom, Son, & Daughter.png|left|thumb|250px|Halsey's memory of presenting Cortana to John.]]Halsey also had somewhat of a unique relationship with [[John-117]]. Some of this may stem from him being the first subject she observed, but she had a great fondness for him and he was her favorite Spartan. Halsey told Cortana she considers him the luckiest and best of the Spartans and apparently also finds him attractive given her embarrassed reaction to Cortana's comments. Halsey was responsible for John's first promotion to Squad Leader as a result of her acknowledging his leadership skills and suggesting it to Mendez. Halsey also had John's full trust and he always did his best to never undermine her authority.

At one point, Halsey decided to test her favorite Spartan's sense of ethics by handing over two sets of data: one concerning [[Avery Johnson]] and how his [[Boren's Syndrome]] supposedly made him immune to the [[Flood]], and the other omitting those details. She ensured that John knew that if the first set was handed over to ONI, Johnson would likely be killed and dissected in order to find a cure to the Flood infection. She estimated that there is a billion to one shot that they could have replicated Johnson's condition, but conversely ONI would do it to save humanity from a greater foe.<ref>'''Halo: First Strike''', ''pages 242-246''</ref> At first, John chose to sacrifice Johnson in order to try and save millions of people out of his duty to protect all of humanity. However, he later reconsidered and eventually destroyed the Johnson data due in part to the sacrifice of [[Vice Admiral]] [[Danforth Whitcomb]] and [[Lieutenant]] [[Elias Haverson]].<ref>'''Halo: First Strike''', ''pages 329-336''</ref>

Later despite John going MIA after the events on Installation 04B, Halsey was sure that he was still alive, and was clearly furious when she found out that the ''Infinity'''s crew had kept his return hidden from her.<ref>'''Halo 4 Prologue'''</ref>
{{Clear}}

==Trivia==
*In ''[[Halo: Reach]]''<ref>'''Halo: Reach''', ''[[Halo: Reach credits|credits]]''</ref> and ''[[Halo 4]]'', Halsey is voiced by [[Jen Taylor]], who also voices Cortana, reinforcing the connection between the two characters. This is also the case in ''Halo Legends'', where [[Shelley Calene-Black]] voices both Halsey and Cortana.<ref>'''''Halo: Legends''''' credits</ref>
*In ''[[Halo: First Strike]]'', it is stated that Dr. Halsey was not keen on losing, as seen when she kept losing at a game of Twenty Questions with her training SPARTANs and soon quit playing.
*She had a knack for embarrassing the SPARTANs with the way she was able to tell them apart through subtle habits in their postures, despite their identical MJOLNIR armor, something no other non-SPARTAN was able to do. Unlike most others, Halsey never referred to the SPARTANs by their numerical designations, but by their names. However, she referred to Daisy-023 as ''"Twenty-Three"'' when trying to convince Daisy to return to the program.
*Two of Dr. Halsey's statements in ''The Package'' are references to similar statements made in the first two ''Halo'' games. She tells John-117 that she slept well "No thanks to their driving," which is echoed in ''Halo: Combat Evolved'' when he tells Cortana he slept well no thanks to her driving. She also tells John, "Don't make a girl a promise...if you know you can't keep it," which Cortana would tell him in ''Halo 2''.
*Halsey's appearance changes drastically from ''[[The Package]]'' to ''[[Homecoming]]''. In ''The Package'', at which point she is aged fifty-two, she is inexplicably depicted as a fairly young woman with short, blond hair and no glasses. This may or may not have been reflected in the later appearance of Cortana, who was created from the replicated neural pathways of Dr. Halsey herself. Her appearance in ''Homecoming'' however, is closer to her description from the books. It should be noted that various concepts in ''The Package'', and ''Halo Legends'' in general, result from artistic license. Her appearances in ''Halo: Reach'' and ''Halo 4'' are much more in line with the description she received in the novels, with the exception of a lack of glasses. In the developer commentary for ''Homecoming'' [[Frank O'Connor]] states "''People tend to think of her as older than she's portrayed... and part of that was simply, you know, it's anime, and they want everyone to be attractive and young. I mean, that's one of the hallmarks anime... I think that IG took the safer of the two routes and sort of disguised her appearance and disguised her age by having it literally obscured by her hair and her glasses and to a certain extent her uniform.''" In ''The Package'' commentary he explains, "''She was definitely one of those back-and-forth conversations [with Casio Entertainment]; 'Can you make her older? Can you make her older?' And eventually we got to this compromise... I think if we were casting a real-life actress we'd cast someone a lot older, but in anime the context is fine and it works.'"''
*Catherine Halsey is also the name of a character in the novel ''The Fountainhead''. In the novel, Halsey progresses into becoming an altruist, thinking of nothing other than the greater good of the majority. In this sense, she is an opposite of the Halsey of the ''Halo'' universe; Dr. Halsey begins by sacrificing the Spartans to buy the UNSC more time, but then changes her mind and does everything she can to save the Spartans, regardless of what happens to the rest of humanity.
*[[Dr. Halsey's personal journal]] is included in ''[[Halo: Reach]]''<nowiki>'</nowiki>s [[Halo: Reach Limited Edition|Limited]] and [[Halo: Reach Legendary Edition|Legendary Editions]]. The journal was mostly written by [[Eric Nylund]] in conjunction with Bungie and 343 Industries, with [[Lorraine McLees]] serving as art director.<ref>[http://halo.bungie.org/misc/enylund_interview_04_2010.html '''Halo.bungie.org''': ''Eric Nylund Interview, April, 2010'']</ref>
*The [[Assembly]] has speculated that Halsey's ruthlessness may have been the result of a chemical imbalance.<ref>'''[[Halo: Reach]]''' [[Data pads|Data pad 7]]</ref>
*Halsey's outfit worn in ''The Package'' can be purchased for one's Xbox LIVE avatar for a price of 240 Microsoft Points.
*The barcode on her badge reads HALSEY when scanned with a barcode reader.
*Originally, in [[S1/Exodus|Exodus]] Halsey was not meant to lose her arm. The writers later decided to remove her arm to add a sense of ambiguity as to who Halsey wanted revenge on.<ref>[http://blogs.halowaypoint.com/Headlines/post/2013/02/27/The-Halo-Bulletin-22713.aspx '''Waypoint''': ''The Halo Bulletin: 02.27.13'']</ref>

==Gallery==
<gallery>
File:HalseyHaloReach.png|Halsey as she appears in ''Halo: Reach''.
File:Ih_halsey_portraitb.jpg|A concept portrait of Halsey for ''Halo: Reach''.
File:Ih_halsey01.jpg|Various early iterations of Halsey's outfit in ''Halo: Reach''.
File:HaloReach - Finale.png|Halsey facing Cortana, her literal brainchild.
File:Halsey_Badge.jpg|Dr. Halsey's [[Office of Naval Intelligence|ONI]] security badge.
File:Halsey_Signature.jpg|Dr. Halsey's signature.
File:Halsey_in_FoR.png|A young Halsey, as depicted in ''[[Halo: Fall of Reach]]''.
File:The Covenant - Halsey.jpg|Another image of Halsey in ''Fall of Reach''.
File:LegendsPackage - Halsey.png|A render of Catherine Elizabeth Halsey in ''[[The Package]]''.
File:Halsey Legends.jpg|Halsey as she appears in ''The Package''.
File:HalseyPod.jpg|Halsey in [[Cryo-chamber|cryostasis]].
File:HalseyPod 2.jpg|Halsey being helped out of her cryo pod by John-117.
File:LegendsPackage-HalseyAndJohn117.jpg|Halsey facing John-117.
File:HalseyJohn.jpg|Halsey watches as John is challenged to an energy sword duel by [[Thel 'Lodamee]].
File:HalseyHomecoming.png|Halsey as she appears in ''[[Homecoming]]''.
File:Halsey n' Daisy.jpg|Halsey facing [[Daisy-023]], who has taken several SPARTAN trainers hostage.
File:Halsey Hornet.jpg|Halsey in an [[AV-14 Hornet]], informing Daisy-023 about the purpose of her flash-clone.
File:Halsey Memory.jpg|One of [[Jacob Keyes]]' final memories of Halsey before he is assimilated into the [[Proto-Gravemind]].
File:Keyes Halsey Memory.jpg|Another one of Keyes' memories of her before he is assimilated within the Proto-Gravemind. She is seen shaking his hand. 
File:H4 Halsey Profile.jpg|A profile of Halsey as she appears in ''Halo 4''.
File:H4-DoctorHalsey-Profile.png|A closeup of Halsey's face in ''Halo 4''.
File:H4 SO Halsey with Jul 'Mdama.jpg|Halsey talking with [[Jul 'Mdama]]. 
File:H4-SOps-Halsey-Librarian.jpg|The Librarian meets Dr. Halsey for the first time.
File:H4-SOps-Halsey-Librarian-1.jpg|Halsey examines a hologram as the Librarian observes.
File:Halsey amputated.png|Catherine Halsey with [[Jul 'Mdama]], note Halsey missing left arm. 
</gallery>

==Note==
<references group="note"/>

==List of appearances==
*''[[Halo: The Fall of Reach]]'' {{1st}}
*''[[Halo: The Flood]]'' {{Mo}}
*''[[Halo: First Strike]]''
*''[[Halo Graphic Novel]]''
**''[[Halo Graphic Novel, Page 122|Page 122]]'' {{Mo}}
*''[[Halo: Ghosts of Onyx]]''
*''[[Halo 3]]'' {{C|Indirect mention only}}
*''[[Halo: Contact Harvest]]'' {{C|As "Charlie Hotel"}}
*''[[Halo: The Cole Protocol]]''
*''[[Halo Wars: Genesis]]'' {{Mo}}
*''[[Halo 3: ODST]]'' {{Mo}}
*''[[Halo: Evolutions - Essential Tales of the Halo Universe]]''
**''[[Pariah]]''
**''[[Human Weakness]]'' {{Mo}}
*''[[Halo Legends]]''
**''[[The Babysitter]]'' {{Mo}}
**''[[Homecoming]]''
**''[[The Package]]''
*''[[Halo: Reach]]''
*''[[Halo: Glasslands]]''
*''[[Halo: Combat Evolved Anniversary]]''
**''[[Terminal/Halo: Combat Evolved Anniversary|Terminals]]''
*''[[Halo: Fall of Reach]]''
**''[[Halo: Fall of Reach - Boot Camp|Boot Camp]]''
**''[[Halo: Fall of Reach - Covenant|Covenant]]''
**''[[Halo: Fall of Reach - Invasion|Invasion]]''
*''[[Halo: The Thursday War]]''
*''[[Halo 4]]''
**''[[Spartan Ops]]''

==Sources==
{{Reflist}}

{{ONI Personnel}}